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Code-division multiple access (CDMA) is a channel access method used by various radio communication technologies. CDMA is an example of multiple access , where several transmitters can send information simultaneously over a single communication channel.
At the time Qualcomm was founded, Jacobs had already been working on addressing telecommunications problems for the military using digital technology to increase the capacity of spectrum. [11] Qualcomm knew that CDMA would greatly increase the efficiency and availability of wireless, but the wireless industry having already invested millions of ...
DS-CDMA (Direct-Sequence Code Division Multiple Access) is a multiple access scheme based on DSSS, by spreading the signals from/to different users with different codes. It is the most widely used type of CDMA. Cordless phones operating in the 900 MHz, 2.4 GHz and 5.8 GHz bands; IEEE 802.11b 2.4 GHz Wi-Fi, and its predecessor 802.11-1999.
The principle of CDMA is based on spread spectrum technology developed for military use during World War II and improved during the Cold War into direct-sequence spread spectrum that was used for early CDMA cellular systems and Wi-Fi. DSSS allows multiple simultaneous phone conversations to take place on a single wideband RF channel, without ...
One key principle of OFDM is that since low symbol rate modulation schemes (i.e., where the symbols are relatively long compared to the channel time characteristics) suffer less from intersymbol interference caused by multipath propagation, it is advantageous to transmit a number of low-rate streams in parallel instead of a single high-rate stream.
Carrier-sense multiple access with collision detection (CSMA/CD) is a medium access control (MAC) method used most notably in early Ethernet technology for local area networking. It uses carrier -sensing to defer transmissions until no other stations are transmitting.
Dealing with co-channel interference from nearby cells is more complex in OFDM than in CDMA. It would require dynamic channel allocation with advanced coordination among adjacent base stations. The fast channel feedback information and adaptive sub-carrier assignment is more complex than CDMA fast power control.
Carrier-sense multiple access (CSMA) is a medium access control (MAC) protocol in which a node verifies the absence of other traffic before transmitting on a shared transmission medium, such as an electrical bus or a band of the electromagnetic spectrum.